This disclosure relates to bacterial diagnostics, and more particularly to the detection of methicillin-resistant Staphylococcus aureus. 
The widespread emergence of methicillin-resistant Staphylococcus aureus (“MRSA”) is a serious clinical problem world wide. S. aureus and especially MRSA today is viewed as one of the major causes of both health care-associated and community associated infections. S. aureus is a commensal bacterium that colonizes the nasal passages, vagina, pharynx, axcillae and/or damaged skin surfaces. Infections can occur with a skin or mucosal breach allowing the access to adjoining tissues and blood stream. Risk is increased by the presence of catheters. S. aureus is unique in its ability to invade normal tissue and cause disease in previously normal tissues at virtually all sites (Boucher et al., CID, 51 (Supplement2): S183-S197, 2010). MRSA causes various infections, for example skin and soft tissues infections, blood-borne infections and pneumonia (Gemmel et al., J. Antimicrob. Chemother., 57: 589-608, 2006). The emergence of S. aureus strains which are resistant to antibiotics poses a challenge to successful treatment. It is viewed that patients hospitalized with S. aureus bacteremia have an unacceptably high mortality rate. Literature available today has indicated that timely selection of the most appropriate antibacterial treatment may reduce mortality. One tool that may help with the selection is rapid distinction of MRSA from methicillin-susceptible S. aureus (“MSSA”) (Brown et al., Pharmacoeconomics, 28: 567-575, 2010).
Although some tools and assays exist for the identification of MRSA, they are less than ideal. As high as 12.9% false positives have been reported for a single-locus commercially available assay (Blanc et al., J. Clin. Microbiol., 49: 722-724, 2011). An evaluation of two single and one double-locus real-time PCR assays for MRSA warns about the high prevalence of “false negatives” and “false positives” (Kolman et al., BMC Res. Notes, 3; 110, 2010). There clearly exits a need for improved MRSA assays.